IâÂÂm slowly trying to figure out why my '84 Suburban C20 (454, dual-air, R134a, CCOT, A6 compressor) will not keep us cool on long trips. The other day, it was 90 degrees in the shade where the truckâÂÂs cold engine was. I hooked the gauges up, and the static pressure agreed with the ambient temperature.
The engine was then started with the auxiliary electric radiator fan on, and the A/C on max (recirc). A minute or two later, 80 degree air was blowing out of the dashâÂÂs center vent. The fan was OFF on the rear air handler. I had hoped for cold air since the whole truck was at ambient.
For some reason, the high-side hose decided to leak at the manifold, and could not be fixed. The engine was switched off, and few minutes later the hose was detached from the high side.
After letting the engine warm up on high idle to the point that the fan clutch engaged (supplementing the electric fan), the high side pressure was steady at 51 psig, and the compressor outlet measured 142 degrees. According to my chart, the pressure would have been ~235 psig. The vent temperature got no lower than 71 degrees. Switching the rear A/C fan on raised the pressures to 51 psig & 150 degrees (263 psig).
Oddly, not only was the accumulator sweating like a pig, so was a lot of the compressor.
Since the system is not cycling, I donâÂÂt think it is LOW on R134a. The next step, after I get a new high-side hose, is to vent some refrigerant, and see if cooling improves. If cooling does not improve, then I have to suspect the compressor is not working hard enough for some reason.
What part of my A/CâÂÂs system would you suspect?
Thanks,
Tom
Lucky you were in the cab. Could have cost you an eye when that let go @ 320+ psi. What brand was that hose?
The up side to this is now we know there was a lot of oil in the system. Those pressures, along with the mess underhood kind of point to a no-flush 134a conversion.
Your fan clutch sounds like it is tired. A good clutch should move enough air on the viscous drive to keep up with things at idle loads. It should roar on a cold start, and blow your hat off. Hopefully you have a fan shroud in place, and it it not missing any huge chunks.
Might as well break the system down now & start from square one. The A6 has a sump, and much of the oil in that system should stay at the compressor. decades ago, the Delco / Harrison rep told us 10% of the weight of the refrigerant charge was "right" for the A6 system's oil charge. Of course back then we would check the oil level on an A6 by cracking the sump plug on a charged system...
I will look for an old book oil charge for that vehicle for you. Flush back to bare metal in the lines & evaporators. Consider upgrading the condensor. Replace the dryer.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
The manifold gauge set was made by Interdynamics.
"Back then" when you checked the oil level by cracking the sump plug, just what were you verifying? The plug appears to be on the bottom, and appears useful only for draining the sump. What am I missing?
Thanks for looking around for an old oil capacity reference- I've gotten a lot conflicting information on how much oil this system is supposed to hold.
Tom
Interestingly, I drove the Suburban down to the quarter-carwash this morning to wash all the oil out from under the hood before doing anything else, and the air conditioner still worked & did not appear to cycle. Vent temp was 70 degrees, ambient 80.
After getting home, I popped the hood to find the compressor still sweating like it was before the hose blew. So I guess the system still has too much oil in it.
Tom
Edited: Sat July 23, 2011 at 10:15 AM by Airstream
There are two aspects of a successful AC repair and diagnostic of a performance (cooling) concern, the amount of refrigerant (fully charged) and the amount of lubricant within the system. Not knowing these values makes for a 'guess-ta-mation' of performance and pressures. To make a valid diagnosis, flush the system....as bohica states...'back to the metal'. Use a good quality flush chemical and air purge to insure removal of all traces of flush. Add the correct amount and type of ac lubricant. Suggest to use a DEC PAG 150 for this system. Insure that the system is fully charged....not the use of several cans and a derived pressure....get the system charged so that one knows the correct quantity of refrigerant. Start with app 90% 134a to 12 specs. Forget the issue of pressures.....they are basically meaningless with a retro fitted system.
A good test for proper charge with this system is to charge with the suggested amount. , Operate the system for app 10-12 minutes with the vehicle @idle, max cool (recirculate),coors open, blower on high. Both front and rear systems should be engaged. Once the system has had time to 'stabilize' determine the inlet and outlet temps of the evaporator. The test should be taken after the orifice tube and before the accumulator inlet. These temperatures should be within 3-5 degrees of each other. A outlet temperature that exceeds the inlet by more than 6-8 degrees requires additional refrigerant. If charge rates are adjusted...the system should be allow to 'stabilize' once more prior to additional testing.
Once more agreement with bohica concerning the fan clutch. A fan clutch should never completely disengage. Clutch engagement is determined by the temperature of the air flow between the radiator and fan clutch temp sensor (face of clutch). A start up the clutch should be heavily engaged and should moderate after a few minutes of operation. Considering the operational time and pressures associated with this test, there should have been good solid clutch engagement. Suggest to disengage the 'supplemental' fan to insure the OE system is functional correct. Then re establish the 'supplemental' fan. This extra fan is a very good idea for retro fitted system...esp when the OE condenser is being used.
Once the system has been serviced, re test all temperature...evap....condenser (inlet and outlet).....vent temps ...ambient temps and post results.
Pressures are good for testing...but surface temps of the heat exchangers are as important. One down side of temp testing...the cost factor. Laser or infra red are almost useless for this procedure. There are several multi-meters on the market that allow for a temp test probe that are 'not break the bank' tools. A good test tool can be purchased from UEI, the single channel is great for basic testing and is quite affordable. Spend the extra cash and obtain a touch type thermo coupler. Their dual channel is a good upgrade. Not sure if site sponsor has access to this tool, but check with them....I am sure they will try to offer a good temp test tool.
Get the system properly serviced and then re evaluate the system.
The issue of the compressor 'sweating' is not that uncommon in some of the earlier vehicles. Lubricant is not the cause....it is the charge rate or flow of refrigerant. The inlet temps of the compressor are cooled (low pressure) to the point that in high humidity areas...they sweat. This was not that uncommon in the A6 mounted on GM or Ford platforms. Not a 'everyday occurrence'...but did happen now and then.
Back to getting the system properly serviced.....and then evaluated.
Good luck.
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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson
Huh, that is a new twist on the ID death kit. Buy a decent Manifold set and save yourself a lot of trouble. That link is for a good solid unit, under a hundred bucks. If the hose was that bad on that ID unit, what else is wrong with it?
Why are you continuing to run a system that has had a catastrophic leak?
I checked my 1985 printed copy of system specs, and the oil charge is listed as 10 ounces. You should put the whole 10 ounces in the compressor sump.
As for checking the oil level, older A6's had a fill plug on the side of the sump. If you have an old (60's vintage) service manual it will have a picture of a wrench on the plug & a description to "look for a drop of oil". Not recommended now of course.
You really need to tear that system down & fix it before you run it any more.
Iceman:
He has a couple of threads on this vehicle here. It is probably way overcharged on oil, sounds like it got 19 ounces of PAG or POE added to the remaining mineral oil charge when it was converted. Nothing is going to change until he opens the system & starts from square one.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
Infra red and laser type test units have proven to be inadequate for measuring temperatures in heat laden areas such as engine bays. They are great for some testing, but we have found over a period of time that a good thermometer with couplers(clamp or touch) is much more efficient when diagnosing an AC system. We have seen test readings that vary as much as 50-60 degrees.
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The strongest reason for the people to retain the right to keep and bear arms is, as a last resort, to protect themselves against tyranny in government.
Thomas Jefferson
Still can't believe all the oil that was recovered, depsite the hose blowing out. You had more oil in there than some OPEC countries have under the sand. Pretty amazing.
Seriously though, get yourself a good set of gauges or you'll just end up with lots of frustration. Site sponsor has a wide variety of quality gauge sets.
Joe
Tom:
That link I posted before is a nice, affordable gauge set. Not the top of the line, but a unit we all trust here. Since you just found out how many people here got started doing their own A/C (dishonest mechanics), take it from someone who has been where you are at - and buy a decent manifold set.
We are all volunteers here, but we do tend to recommend the site sponsor. That link does go to the site sponsor, but buy from whoever you like. Just buy a decent gauge set.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
Thanks for the support. Helps to keep things running around here.
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Basically, you need to tear down the whole system and start over. The old style condenser can be flushed and so can the front evaporator.
Install a new orifice tube and drier. Vacuum down the system for about an hour. Then, add the refrigerant oil in the proper amount followed by refrigerant.
It is not going to blow ice cubes, but it will keep you cool. I have an 85 model with an entire retrofit and it does just fine.
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Grove Automotive Group, Inc.
An Alabama Corporation
One of the requirements for a 134a conversion is the HPCO. That switch should drop the compressor out around 400 to 420 psi.
Obviously if it is cycling on the HPCO, you have a problem. What Iceman means is you need the full charge in the system to operate properly, and sometimes that means pressures that are higher than they were with the original R12 charge. That "80%" number was intended to hold the pressures down to near R12 levels.
Since your rear system is an aftermarket unit, the charge levels are a big unknown anyway. I suspect the system may hold more than an OEM rear because of plumbing differences. You will need to watch the pressures, and monitor the evaporator line temperatures for optimum performance.
Don't be surprised by high side pressures that are more than 3x the ambient temperature during full load testing.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
The new gauge set arrived just a little while ago.
Although it has yet to be hooked up to the Mighty Suburban, I am incredibly impressed with what I see in comparison to the last set of gauges I had. Although the manifold appears similar in appearance to what I had, the hoses/fittings appear to be of a quality head-and-shoulders above what blew out before. Mastercool's hose description, if nothing else, reads better than than the lack of description the last set had. If nothing else, the new hoses had a better "feel" to them (as in not potentially blowing apart later) than my last set. It will be nice to have gauges with R134a markings.
To be honest, I ordered this particular item from Tim because of Brad's posts about having the right equipment to do the job got to me. I'm not used to the abuse (I've yet to make a mistake...ever...just ask me). But Brad gets a big thumbs-up on this one. Tim does too for making it available.
If nothing else, I never even noticed the package was supplied with 72-inch hoses when it was ordered. It's just a bonus day here in AL.
I expect great results tomorrow or the next day. But if that does not happen, it won't be because of faulty test equipment.
Tom
I've never regretted spending money on good tools... it's only when I've cheaped out did I have regrets. And you've definitely purchased from the right place.
I still have my original R-12 gauge set that I first started out with sometime in the early 1980s. The low side hose still has gouges from dancing on the fan of a Lincoln 460 V-8 (those things had such thin shrouds), but it's still good. I do have a replacement hose, still brand new, haven't had the need for it. That gauge set has gotten knocked around quite a bit and is still going strong.
Joe
Aye, that's the ticket. Always nice to have the long hoses - makes duct taping the gauge set to the windshield so much easier!
As for "taking the abuse" - I thought all Airstream owners were used to it. Now the guy with a vintage IHC Travelall towing a vintage Airstream? He is just a glutton for punishment.
Having a gauge set you trust takes the guesswork out of things like setting the cycling switch. Nothing like a 10 psi error in a gauge set to make you think there is a cooling issue when a simple cycling switch problem is making 60f vents.
Hopefully the rest of the repair will go smoothly for ya.
B.
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"Among the many misdeeds of the British rule in India, history will look upon the act of depriving a whole nation of arms, as the blackest."
~ Mahatma Gandhi, Gandhi, An Autobiography, M. K. Gandhi, page 446.
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